Respiratory mucous glycoprotein (MGP) is secreted in a variety of acute and chronic disease states: secretion is strongly influenced by inflammatory mediators, but the mechanics by which MGP is influenced are unclear. The capacity of activated human neutrophils (PMN) to stimulate respiratory mucous glycoprotein secretion from human airways in vitro was studied. Purified PMN activated with opsonized zymosan stimulate the release of MGP from human airways in a dose-dependent manner. One neutral protease, neutrophil elastase in nanogram/ml concentrations, stimulates the release of antagonists do not block the effect of supernatants from activated PMN and MGP secretion. Current work is directed at identifying the products released during neutrophil activated which stimulate MGP secretion. Information available to date suggests that the molecule responsible is large (115,000 molecular weight) and work is progressing on HPLC DEAE Ion exchange column and elutes in 0.2 m NaC1. It has a PI of about 6.8. The significance of this work lies in the identification of inflammatory mediators which might stimulate MGP secretion in vitro in such states as acute and chronic bronchitis, asthma, and cystic fibrosis.